High-Purity CO ₂ Capture from Blast Furnace Top Gas: Optimal Design Trade-Offs between Hybrid VPSA–Cryogenic Distillation and Amine Scrubbing

High Resolution Image Download MS PowerPoint Slide Vacuum pressure swing adsorption (VPSA) has been proposed for CO 2 capture from blast furnace top gas owing to its high CO 2 partial pressure, but prior studies have rarely achieved the pipeline-specification purity. This work develops and systematically evaluates a hybrid VPSA–cryogenic distillation process to overcome this limitation and benchmarks it against amine scrubbing using validated process models. Multistage pressure equalization increases CO 2 purity from 69% in a 2-bed to 87% in an 8-bed/4-stage VPSA while sustaining 90% recovery with zeolite 13X. Subsequent cryogenic distillation further raises purity to 99.9% with electricity use of 265–333 kWh/tonne CO 2, more than a 50% reduction compared to reflux-intensive VPSA reported in the literature. Cost analysis identifies an optimal VPSA outlet purity of 78% as the most economical threshold; additional stages increase capital without proportional benefits, whereas fewer beds raise energy penalties from added CO compression and cooling. Amine scrubbing with monoethanolamine is 34–58% more cost-effective than the VPSA–cryogenic process across regional energy prices, enabled by fast absorption kinetics and lower capital requirements. It is particularly economical in the U.S., where the steam-to-electricity cost ratio is lowest. The VPSA–cryogenic process becomes competitive only when electricity falls below $0.06/kWh and steam exceeds $19.9/MMBTU. These results establish design thresholds and cost–energy trade-offs that guide CO 2 capture strategies for steelmaking decarbonization.